In the meantime, hardware characteristics and deploying environments also bring unique reliability challenges to the IRS.
The IRS consists of massive passive “meta-atoms" that are made of two-dimensional (2D) metamaterial [1]}, [2]}, which may result in a high failure probability due to large system scale and dense interconnections of tuning circuits [3]}, [4]}.
On the other hand, the short wavelength of mmWave band makes the IRS vulnerable to the blockages with comparable sizes like dirt, particles, and flying debris in outdoor deploying environments [5]}.
Reflecting characteristics of the IRS also make it more sensitive to failures than conventional MIMO systems.
It is reported in [6]} that the power gain provided by the IRS scales up with the square of the number of reflecting elements.
Therefore, the IRS also suffers from “squared power loss" since faulty reflecting elements could cause twice attenuation during incidence and reflection.
It is also reported in [4]} that faulty reflecting elements may result in various radiation pattern distortion issues like degraded directivity, increased side-lobe level, and beam misalignment.
In summary, the existence of faulty reflecting elements could significantly degrade system performance, which necessitates diagnostic techniques for locating faulty reflecting elements and retrieving failure parameters for calibration purposes.
